The U.S. military has begun evacuating some people in the area, including from the Marine Corps’ recruit-training depot at Parris Island, S.C., which sits in a marshy area on the coast. The recruits and the Marines training them are being bused to the Marine Corps’ logistics base in Albany, Ga.

“I have determined the safest course of action is to evacuate,” said Brig. Gen. James Glynn, who commands Parris Island. “For everyone’s safety, I have issued the evacuation order well ahead of the storm in an effort to ensure everyone is able to seek refuge before the storm impacts the area.”

Defense Secretary Jim Mattis told reporters at the Pentagon on Tuesday that he was being updated every day on the status of the hurricane and plans for the next 24 and 48 hours. He also is receiving reports throughout the day about preparations involving the military.

The Marine Corps, with its large concentration in North Carolina, could be especially affected. Camp Lejeune, one of the service’s largest bases, is on the coast close to where the hurricane could come ashore. Capt. Joseph Butterfield, a Marine Corps spokesman, said many personnel living there are being encouraged to leave, while essential ones are preparing to ride out the storm so that they are positioned to help others afterward.

Florence could cause serious damage up the coastline, where the Navy sent nearly 30 ships to sea from the port of Norfolk on Monday to get out of the way of the storm before it strikes.

It also could cause significant flooding farther inland, where bases such as the Army’s Fort Bragg, in North Carolina, are hubs of operations and home to tens of thousands of service members.

The military also has begun to move some aircraft, especially fighter jets, away from the coastline.

The Air Force, which operates F-22 Raptors and other jets from Joint Base Langley-Eustis near Hampton, Va., began sending planes to Rickenbacker Air National Guard Base in Ohio on Tuesday.

The Coast Guard started positioning rescue helicopters, equipment and people to best respond to the storm several days ago, and brought in some assistance from other parts of the country, officials said.

“Wednesday is the last full day to prepare for #Florence,” the Coast Guard said in a tweet. “It is crucial for residents and visitors in potential impacted areas to listen to local and state officials. If you’re being told to evacuate, please do so.”

The Pentagon sent a small team of Defense Department personnel to an emergency operations center in Raleigh, N.C., on Monday to carry out an assessment and coordinate with state officials, said Col. Rob Manning, a Pentagon spokesman.

The military also is making preparations for the Federal Emergency Management Agency to use Fort AP Hill, a training base about 45 miles north of Richmond, as a staging area for any relief effort.

On Tuesday, the Army also tweeted that FEMA had begun setting up trailers at Fort Bragg.